Plastic catheters have been used for access to veins, arteries, the epidural space and other neural sheath spaces for decades. The catheters are typically introduced through the skin (“percutaneous”) either over the outside or within a needle. Alternately they may be introduced over a guide wire that was introduced through the skin inside of a needle. The objective for all medical catheters is to enter a specific space (vein, artery, epidural space, dural space or neural space) and to lie in that space so that fluids or pharmaceuticals that flow from the distal tip of the catheter are delivered to the specific space. The most common of these are IV catheters delivering intravenous fluids and pharmaceuticals into the venous blood.
All percutaneous catheters enter the body through the skin at a puncture site. A catheter then traverses through the subcutaneous tissue for a distance (typically 0.25 to 0.5 the length of the catheter) before entering a vein or artery. The same needle that pierced the skin then pierces the vein or artery and the plastic catheter is advanced off of the needle and into the vein or artery until the catheter hub connector abuts the skin. For example, IV catheters of 1.25 inches or less will typically end up with less than half of the catheter in the vein when the insertion is complete. Therefore, if a catheter is inadvertently pulled even a short distance out of the skin, or if the skin anchoring the catheter is moved relative to the vein, it could result in the tip of the catheter “popping” out of the vein and “blowing” the IV.
When an IV or arterial catheter is fully and properly inserted, the catheter is not visible and the only portion left showing outside the skin is the hub and the tubing connected to the hub. Not surprisingly, since the hub is the only part of the catheter that is accessible, clinicians have used various taping methods to secure the exposed hub and the tubing to the skin adjacent or lateral to the hub, in order to secure the device. In addition, hundreds of catheter-anchoring devices have been described in patents and patent applications. To the instant inventors knowledge, every single one of the prior art catheter anchoring devices secures the hub or tubing, to the skin adjacent the hub.
The fact that catheters are secured to the skin adjacent the hub is the genesis of several problems well-known to plague IV and arterial catheters. The skin is a very stretchy and movable organ. When tension is applied to the skin, it stretches and moves somewhat independently from the skin nearby. Additionally, it also easily moves relative to the underlying skeletal structures such as muscle and bone, because of the loose connective tissue layer that connects the two together. Most of the veins used for IV access lie within this loose connective tissue layer and are thus loosely connected to the skin and also loosely connected to the underlying skeletal structures. When the overlaying skin stretches and moves, it causes the loosely connected adjacent veins to also move. The skin adjacent to the hub is not overlaying and therefore not connected to the portion of the vein that includes the vein puncture site and the catheter tip. Therefore, the vein puncture site and the vein wall adjacent the catheter tip do not move when the skin adjacent the hub is stretched or pulled as occurs with the prior art catheter securing techniques. Many people, especially the elderly, have excess or loose skin which makes this problem even worse.
When the catheter hub that is anchored to the skin adjacent the hub (as in the prior art) is pulled or if the skin adjacent the hub is pulled, the skin can stretch, easily allowing a 0.25 inch movement of the catheter out of the skin puncture site. This also results in a 0.25 inch movement or more of the catheter relative to the vein puncture site which is not under-laying the skin attached to the hub. The first 0.25 inches of movement is due to the skin stretching and laxity between the hub and the skin. An equal or greater movement is caused by the movement of the skin adjacent the hub relative to the vein that is 1-2 inches away from the hub and connected only by loose connective tissue. A total catheter movement of 0.5-0.75 inches may occur at the vein puncture site. IV catheters are also frequently placed near the wrist, where flexion of the wrist creates a movement of the skin that is very similar to the stretching of the skin.
Catheters can also be pulled out by twisting the hub about a vertical access rising perpendicularly from the skin. The twisting action can be caused by an inadvertent lateral pull on the IV tubing. The twisting action can “lever” the catheter out of the skin without stretching the skin.
It is apparent that in the normal course of having an IV with the prior art securing methods, the catheter will be pulled 0.25 inches out of the skin and 0.25-0.75 inches out of the vein many times each day. It then usually slides back into the skin and vein without apparent incident. This catheter movement in and out of the skin can be referred to as “pistoning.” However, the negative consequences of the pistoning of the catheter in-and-out of the skin and vein caused by securing the catheter hub to the skin adjacent the hub are significant and relatively frequent:
1. When the catheter is pulled partially out and the vein or artery does not move equally in the same direction, the tip may pop out of the vein or artery puncture site, causing a “blown” or unusable IV or arterial line.
2. Pistoning can result in the relatively stiff tip of the catheter repeatedly poking the wall of the relatively fragile vein until it pokes through the wall and “blows” the IV.
3. When the sterile catheter pulls out of the skin by 0.25 inches or more, it is instantly exposed to a variety of skin bacteria incubating in the warm blood and serum that has oozed from the IV puncture site and is captured by the occlusive dressing that is frequently applied to the IV site. When the catheter is then reintroduced back through the skin, these bacteria which are now coating the catheter, are transported through the skin and deposited into the subcutaneous tissue where they can cause a “line infection.”
4. The 0.25-0.75 inch pistoning of the relatively sharp catheter tip against the fragile wall of the vein or artery can abrade the endothelial layer from the vein or arterial wall. This exposes the deeper structures of the vein or artery to the blood. These deeper structures are well known to be thrombogenic, meaning that the injured but not perforated vein or artery may cause a blood clot to form within the vessel.
5. Twisting of the hub relative to the catheter not only causes pistoning of the catheter but also may kink the catheter, preventing fluid flow.
Central venous catheters, epidural catheters and neural block catheters are typically much longer than IV or arterial catheters. Central venous catheters typically do not pop out of the vein or “blow” by poking out of the vein, however, they may kink occluding flow or piston in-and-out increasing the probability of line infections. Epidural and neural sheath catheters can pull out and become dislodged from the proximity of the nerve and thus become non-functional. These catheters are also easily kinked and thus occluded.
Blown IVs, kinked IVs, line infections and venous or arterial thrombosis are all well-known complications of venous and arterial catheters. Dislodgement or kinking of epidural and neural catheters are also well known problems. Clearly there is a need for a better catheter anchoring device that prevents these well-known problems associated with prior art catheter securing devices and adhesive tape techniques for anchoring medical catheters.